U.S. Treasurys, Japanese Yen Part Ways

By

Cynthia Lin

Updated Feb. 8, 2013 4:12 p.m. ET

For years, the rule was simple: Whatever direction the Japanese yen took, so too would U.S. Treasurys. Now, investors need a new rulebook.

The two markets, each regarded as safe havens by global investors, have traveled hand in hand for much of the past decade. They would both rise whenever financial threats or waning global growth prospects made investors averse to risk, and then they'd fall whenever the picture improved and risk appetites recovered. But as the two countries' central banks push aggressively to revive...